A terminal block of the aforesaid type is usually mounted outdoors. Even when surrounded by a protective housing, it is exposed to rain, snow, sleet, ice, temperature fluctuations, dirt, insect infestation and similar conditions that may adversely affect the electrical connections between the service wires and electrical connectors, which may be and usually are of the insulation displacing type, within the blocks. To minimize incursion of foreign matter, viscous sealing material has heretofore been provided within interior areas of prior art terminal blocks. The protection afforded by the sealant material usually is adequate for as long as the original connections between the service wires and the associated insulation displacing connectors remain undisturbed, but has heretofore rapidly decreased in proportion to the number of times that the connections are re-entered (i.e, broken and reestablished) by a telecommunications craftsperson. The decreasing protection is due to the fact that each re-entry displaces some of the sealant and causes the formation therein of voids that permit ingress of air, dirt, moisture, insects and the like. The use of sealant of the gel type minimizes the size of such voids but does not entirely eliminate their formation. Reliable protection of the terminal block against surge (i.e., overvoltage and/or overcurrent) conditions is also highly desirable since in the absence of such protection lightning strikes, engagement of the telephone wires by power lines, or similar conditions can severely damage the terminal block and components or structures adjacent thereto and/or connected therewith.